Access to data networks, for example the internet, is typically achieved using a conventional personal computer (PC) terminal, which has a large high resolution display and relatively high data transmission bandwidth. In order to communicate with the network concerned the user of the PC typically inputs a network address via a keyboard or other input device, such as a mouse. These devices enable long and complex network addresses to be input to the PC relatively easily so that network locations may be accessed.
A recent development in network, and particularly the internet, access is the standardization of a wireless application protocol (WAP), using the so-called “wireless markup language (WML)”. The WAP system enables terminals with small displays, limited processing power and low data transmission bandwidth (for example digital mobile telephones and similar devices) to access and control services and content in a network such as the internet. WAP is a layered communications protocol that includes network layers as well as an application environment including a browser (network communication software). WML uses simple syntax and limited vocabulary in order to make it suitable for controlling communications with a network by a user having access to a portable device.
Whilst the ability to use smaller terminals can be a major convenience to a user, it can be inconvenient to access complex network addresses using a relatively simple keypad input device. For example, a mobile telephone has a keypad primarily intended for inputting telephone numbers, and so input of other characters can become complex and tiresome. It has been proposed to overcome this disadvantage by providing voice control of the user interface. In such proposed systems, automatic speech recognition (ASR) systems are used in order to recognise voice inputs and produce the network location address on the basis of the recognition.
However, in order that a portable device with low processing power is able to implement such voice control, the vocabulary that is stored to be recognised will necessarily be small. Therefore it has been proposed that automatic speech recognition (ASR) be carried out by the network itself. However, this requires the opening of a voice channel between the portable device and the network. This has the obvious disadvantage that the voice channel itself may introduce distortion echoes or noise, thereby degrading the recognition performance. Also, the speed of the voice recognition will be severely compromised.